Andrew Coppin <orp### [at] btinternetcom> wrote:

> Has anyone ever seen that funky transparent plastic that turns rainbow
> colours when you try to bend it?
> 
>   1) does anyone know how this stuff works?

The effect is called photoelesticity, whereby the optical axis of a
material changes depending on the mechanical stress applied to it. 

It's as if each part of the material is a piece of polaroid, but its
axis of polarization changes according to how much that part is under
stress.

You get the coloured effect when you put the material between crossed
polarizers. Look, for example, at:

http://technology.open.ac.uk/materials/mem/mem-photo.html

>   2) can it be simulated with POV-Ray?

I guess it's the same kind of problem as in the polarization thread. A
lot of work!

-- 
Kaveh

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